<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>打勾</title>
  <style>
    .box {
      position: relative;
      display: inline-block;
    }

    input[type="radio"] {
      opacity: 0;
    }

    label {
      position: absolute;
      left: 0;
      top: 0;
      width: 20px;
      height: 20px;
      border: 1px solid #999;
      /* border-radius: 50%; */
    }

    input:checked+label {
      /* background-color: #ff3334; */
      /* overflow: hidden; */
    }

    input:checked+label::after {
      position: absolute;
      content: "";
      width: 100%;
      height: 50%;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -20%) rotateZ(-45deg);
      transform-origin: 0 0;
      /* background-color: #ff3334; */
      /* border-radius: 50%; */
      border: 2px solid #ff3334;
      border-top: none;
      border-right: none;
    }
  </style>
</head>

<body>
  <div class="box">
    <input id="item2" type="radio" name="item">
    <label for="item2"></label>
  </div>
</body>

</html>